Recently, portable apparatuses such as a digital camera, a mobile phone, a tablet terminal, and a notebook computer spread broadly. Most of these kinds of apparatuses are driven by a battery.
When a second battery is used as the battery, the battery can be used repetitively by charging. When the battery is charged, power supplied from a commercial power supply or a charger is used. In a large number of apparatuses driven by the battery, “operation charging” in which the battery is charged while an apparatus body is operated in a state in which the apparatus is connected to the commercial power supply or the charger is enabled. During the operation charging, generally, surplus power obtained by subtracting consumption power necessary for an apparatus operation from the supplied power is used for charging the battery. In addition, during the operation charging, the power necessary for the apparatus operation is used preferentially from an external power supply such as the commercial power supply and is not supplied from the battery.
Methods of feeding power to the apparatus driven by the battery are various. In recent years, “universal serial bus (USB) feeding” to supply power through a USB cable has increased. For example, an electronic still camera in which a digital camera and a personal computer are connected by the USB cable and transmission of image data and charging of the battery are executed at the same time through the USB cable has been suggested (for example, refer to Patent Document 1). However, depending on a connection destination of a USB port, the maximum current standard may be as low as 500 mA. In this case, because only an amount obtained by subtracting a current value necessary for the apparatus operation is allocated to the charging, charging efficiency is not good (for example, refer to Patent Document 2). That is, the operation charging has a problem in that sufficient charging of the battery cannot be executed for consumption of the power by the apparatus operation.
In addition, during the apparatus operation, appropriate power supply may be necessary. For example, the appropriate power supply may be necessary during an imaging operation in the digital camera or a transmission operation of image data for an external apparatus such as a personal computer. In a state in which the battery is drained, the apparatus operation should be executed using only the feeding power. However, when the maximum current standard is low as in the USB feeding, a current necessary for the transmission operation of the image data may not be obtained. In this case, the data transmission should be started after the charging of the battery is executed.
In addition, in the digital camera, an operation such as driving of a lens barrel also needs large power more than a predetermined rating of the USB cable. For this reason, an electronic apparatus such as the digital camera in which, when it is confirmed that necessary power cannot be supplied from the charging battery, the necessary power is supplied from the charging battery after the charging is executed has been suggested (for example, refer to Patent Document 3).
As such, depending on the remaining capacity of the battery, the apparatus operation that is enabled during the charging is restricted. The apparatus operation is restricted until the battery is charged, regardless of a power supply being connected. Therefore, usability is not good.
For example, a wireless communication apparatus in which, if the remaining battery capacity decreases at the time of wireless communication using the battery, a transmission output level is decreased, power consumption is suppressed, and a communication time is increased has been suggested (for example, refer to Patent Document 4). However, in the wireless communication apparatus, if charging efficiency of the battery at the time of the operation charging is not improved, a problem of the restriction of the apparatus operation cannot be resolved in a state in which the operation charging is enabled.